Currently, in a process of forming a microstructure, such as a metal pattern, an insulation layer or a separation membrane, used to manufacture an electric/electronic device, an optical patterning (photolithography) method, based on exposure and etching, is generally used. However, this optical patterning method is an energy-intensive high-cost manufacturing technology including several complicated processes. Moreover, the optical patterning method is problematic in that waste gas, waste water and the like are discharged during exposure and etching processes, thus causing environmental pollution. Therefore, it is required that a simple, low-cost and environment-friendly process be developed instead of the optical patterning process based on exposure/etching.
Thus, a process of preparing an electrode material by forming a metal coating layer on a conductive polymer such as poly(ethylenedioxythiophene) doped with poly(styrene sulfonic acid) has been developed. For example, Japanese Patent Publication Nos. 2003-197028 and 2004-238730 disclose a conductive particle including a resin-made spherical core material whose surface is provided with a plated layer. A conductive polymer is advantageous in that it can be easily patterned by a solution process such as screen printing, but is disadvantageous in that it is difficult to obtain reliable electric resistance because its conductivity is far lower than that of a metal material.
Therefore, research into a material which can be applied to a solution process of easily forming a pattern using a metal material having excellent conductivity is required. For example, a process of forming a metal material into metal nanoparticles and then dispersing the metal nanoparticles in a solvent is being spotlighted. When a metal material is formed into metal nanoparticles, the melting point of the metal material can be remarkably lowered, thus providing the basis for forming a conductive film for an electrode using low-temperature heat treatment.
However, when metals such as copper (Cu), nickel (Ni) and the like, which are generally used as cheap electrode materials, are formed into metal nanoparticles, the metal nanoparticles become an obstacle to sintering behavior at the time of heat treatment because they tend to be thermodynamically oxidized, with the result that it is not easy to form a high-conductivity film. Further, silver (Ag) and gold (Au), which are also used as electrode materials, do not have such a problem of oxidization, but they are expensive, so their usefulness is limited. Therefore, it is required to develop a novel electrode material which is cheap and can provide high conductivity.